High‐performance thin‐layer chromatography with atmospheric solids analysis probe mass spectrometry for analysis of gasoline polymeric additives

Abstract

Rationale The offline coupling of high‐performance thin‐layer chromatography (HPTLC) with atmospheric solids analysis probe mass spectrometry (ASAP‐MS) was evaluated for the characterization of polymeric additives in gasoline. Methods A protocol was developed to optimize the ion signal. A glass capillary was moistened with deionized water, and then dipped into silica gel scratched from an HPTLC plate. The capillary tube was fixed to the ASAP holder and introduced into the ionization source for analysis by MS. Silica gel, reversed‐phase C18 and cellulose stationary phases were evaluated. Results The effect of the stationary phase and the nature of analyte were evaluated using polypropylene glycol and polyisobutylene succinimide polyamine as analyte molecules. The optimal ionization conditions are significantly different between ASAP and HPTLC/ASAP‐MS analyses. In particular, a higher desorption gas temperature was required to produce ions from the silica gel HPTLC plate. The presence of the stationary phase reduces the internal energy of the ions and limits the fragmentation. Conclusions HPTLC/ASAP‐MS is a very fast and efficient technique for the analysis of polymers in formulated fuels. Good ionization efficiency was obtained with all investigated stationary phases.

Elucidation of Low Molecular Weight Polymers in Vehicular Engine Deposits by Multidimensional Mass Spectrometry

“…The composition of polymer blends that give convoluted mass spectra could be effectively visualized by postacquisition Kendrick analysis using fractional base units. Our study also affirmed that different mass spectrometry techniques can be used cooperatively, either in series (as in LC-IM-MS) or in parallel (as in MALDI-MS vs ASAP-MS vs LC-MS), for the elucidation of complex fuels and fuel byproducts; this approach, which had been applied previously to fuels and fuel additives, ,,,, was successfully extended in this study for the first time to vehicular engine deposits. Overall, specific low molecular weight polymer structures could be detected and identified in a completely unknown sample that was examined using various separation methods and accurate mass measurements.…”

“…To circumvent the issue, ASAP-MS was employed, which can ionize solid samples via thermal desorption and/or thermal degradation depending on sample volatility and ASAP temperature. ASAP-MS has been performed by other groups to examine crude oil and gasoline additives, ,,, focusing on the molecular weight distribution (MWD) of the products , and characterization of the ion distributions resulting from known, authentic polymeric additives in petroleum. , Here, the ASAP-MS method is applied for the first time to unknown solid vehicular engine deposits to characterize the types of polymers present in such samples and also assess their molecular structure identities. ASAP-MS experiments were run using thermometric gradient ramping or isothermic conditions.…”

“…ASAP-MS has been performed by other groups to examine crude oil and gasoline additives, 25,26,40,41 focusing on the molecular weight distribution (MWD) of the products 40,41 and characterization of the ion distributions resulting from known, authentic polymeric additives in petroleum. 25,26 Here, the ASAP-MS method is applied for the first time to unknown solid vehicular engine deposits to characterize the types of polymers present in such samples and also assess their molecular structure identities. ASAP-MS experiments were run using thermometric gradient ramping or isothermic conditions.…”

“…Various mass spectrometry methods have been used for the analysis of petroleum-based fuels and lubricants, , including tandem mass spectrometry (MS/MS), liquid chromatography-MS (LC-MS), ion mobility-MS (IM-MS), and atmospheric solids analysis probe-MS (ASAP-MS). − The most recently introduced ASAP-MS technique allows for the direct analysis of liquid and solid samples with little to no sample preparation . This feature makes ASAP-MS particularly appealing for the analysis of fuels and fuel byproducts, as it bypasses solubility issues and time-consuming extraction processes. , MS/MS, LC-MS, and IM-MS can also provide useful analytical information about these samples; specifically, MS/MS can reveal connectivity insight about the ions observed by MS, whereas the LC and IM event add necessary separation dimensions to deconvolute complex spectra. ,, Several of these techniques can also be interfaced with one another to reduce sample complexity, speed up the analysis, and augment the derived structural information. For example, ASAP-IM-MS has been employed for the rapid analysis of lubricants, while LC-MS/MS has aided the identification of the functional groups in fuels .…”

“…24 This feature makes ASAP-MS particularly appealing for the analysis of fuels and fuel byproducts, as it bypasses solubility issues and time-consuming extraction processes. 25,26 MS/MS, LC-MS, and IM-MS can also provide useful analytical information about these samples; specifically, MS/MS can reveal connectivity insight about the ions observed by MS, 27 whereas the LC and IM event add necessary separation dimensions to deconvolute complex spectra. 18,27,28 Several of these techniques can also be interfaced with one another to reduce sample complexity, speed up the analysis, and augment the derived structural information.…”